Solenoid



w. A. RAY

soLENoID v April 8, 1941.

Original Filed Oct.

INVENTOR.

A TTORNEY Reissued Apr. 8, 1941 SOLENOID william a. nay. Glendale, cam., signor m General Controls Company. a corporation of California Original No. 2,096,196, dated November 2, 19,37, Se-

rial No. 105.400, October 13, 1936.

Application for reissue Aillllst 5, 1938, Serial No. 223,297

(Cl. 17E-338) 4 Claims.

This invention relates to an improved construction for an electro-magnetic operator, commonly termed a solenoid. The present invention rey lates to improvements in the construction of those devices generally disclosed byme in my applications Serial No.635,886 filed October 3, 1932, now Patent No. 2,096,763 of October 26, 1937, and Serial No. 92,748 -led July 27, 1936, now Patent No. 2,098,195 of November 2, 1937. l

In the construction and manufacture of a suitable electro-magnetic operator for use upon alternating current, I have experienced considerable diiilculty in ridding the device of humming. For example, in assembling the control device disclosed in my Patent No. 2,046,882, of July 7, 1936,

it was found that sometwo to four hours .time

was necessary to assemble the solenoid valve 29 inthe structure shown in said patent to ensure that the solenoid would be free from hum. This assembly time for this single unit raised the assembly cost for the valve structure of said patent beyond all practical reason; l

After considerable investigation into the cause of the humming and after many trials in an attempt to overcome this undesirable characteristic, I have at least found a construction which obviates the humming, enabling the electro-magnetic operator to be assembled as rapidly as an assembly mechanic can put the proper parts together. This has enabled the assembly of the aforementioned valve of my patent to be made with much greater ease, since the time required in connection with the magnetic operator 29 is a matter of minutes, as compared to hours.

Briey summarizing the results of my investigation into the causes of humming, it was my finding that humming was due to transverse displacement of one end of the solenoid plunger. This occurred even though the other end of the plunger was xed against such transverse movement and even though all parts of the electromagnetic operator, including the washers, plunger and associated metal parts were carefully machined to tolerances so restricted as to be impractical in commercial production.

I found that it was necessary to keep the plunger axially aligned in the magnetic center of the axial passage through the coil of the electro-magnetic operator. This centering I accomplished in a very simple manner, as will presently appear hereinafter, wherein I have disclosed the preferred-construction embodying the discovery of this invention.

It is in general the broad object of the present invention to improve upon the construction of an Y electro-magnetic operator to the end that hum- Ul A ming of said operator, when utilized in conjunction with alternating current, is eliminated.

A further object of the present invention is to provide an improved solenoid construction enabling an effective electro-magnetic operator to be constructed by commercial manufacture to provide a cheap, readilyassembled and yet satisfactory operator.

The invention includes other objects and'features of advantage, some of which, together with the foregoing, will appear hereinafter, wherein the present preferred construction of this invention is set iorth.

' In the drawing accompanying and forming a part hereof:

Figure l is a section taken through a solenoid structure including the present preferred construction. o l

Figure 2 is a cross section through the structure of Figure 1.

Figure 3 is a cross section through a solenoid in which the solenoid plunger floats. y y

The actuator of the present invention is provided with abase 6 having a threaded extension I so that the actuator can be suitably attached to a housing, such as that including a valve or other device to be operated. A non-magnetic tube l of brass, Monel or the like is secured to the base l. An insert I2 is secured as at I3 to the tube, the insert including an extension I4 thread' rolled in to t this groove and to retain the magf' netic ring in place. An insert 2| of magnetic material is carried on the insert I2, the insert 2i projecting beyond the insert I2 and being formed at 22 to center the solenoid plunger generally indicated by numeral 2l. The solenoid plunger is a composite structure, including an youter magnetic shell 23 or primary core approximating in size the ring I8. Mounted within andadjacent the upper end is a non-magnetic plug l. providing a `shading ring. Inserted within this plug is a magnetic plug 26 providing a secondary core. vThe magnetic plug 26 and non- 'place by a sleeve 2l of magnetic material screwed into the bottom of the sleeve Il. Stud Il has a head 2l thereon against which rests a light spring Il. 'I'his spring urges stud 2l upwardly to permit the plunger to rise before it 'begins to lift stud 2l and the structure attached thereto. for example, a valve.

The electromotive force is supplied by a coil II formed upon a spool1 Il. The spool Il is posltloned between magnetic washers 3i and Il, these washers being mounted upon and includ- `ing angular portions Il extending along the tube I.

In operation, the current ilow through the coil reaches a maximum ilow at the peak of the sine wave, and a minimum or zero ilow at the end of each haii' cycle. Actually, there is a large ow of current provided in one direction for a fraction of a second, followed by cessation of current flow when the half cycle changes or the current reverses. The present invention enables an effective force to be maintained upon the solenoid plunger at all times and even though the current for an instant is zero and subsequently reverses. This substantially constant flux flow to the plunger enables the humming noise to be overcome.

It is the discovery of the present invention' that-the humming noise is due to vibration of the solenoid plunger, particularly in that region adjacent the stud 21. Since the plunger is positioned at the other end by engagement of parts 22 and 2l, I have found that by placing a ring 4I oi non-magnetic material, such as copper, brass, or dural, around the base of the solenoid plunger, the humming can be obviated. `'I'his I attribute to the shielding eifect. on the base of the plunger, from the adjacent lines oi' iiux from the washer Il and its portion 3l.

It is very dimcult to manufacture an electromagnetic operator of the type herein dealt with which is symmetrical about the solenoid plunger axis. For example, any slight excess thickness in one side of angular portion Il will result in a greater no w of magnetic lines of force from. that side than from the opposite side. As a consequence, the solenoid plunger attempts to position itself in the magnetic center. However,

since the device is being operated upon alter-` nating current, the flux lines are constantly changing. with the result that the plunger is always attempting to follow this change and take up a new position. By providing the ring l Il about the base of the plunger, the inequalities are more or less equalised, so that such careful attention to super-accurate machining is not necessary. As a matter of fact, I have i'ound` that super-accurate machining without the present invention .and the structure evolved, thereby was not suflicient, for solenoid operators manufactured under the most careful machin lng and super-tolerances were extremely disappointing in that theyhummed just as loudly as those taken from the commercial assembly line.

The present invention therefore enables a re1- to wom s dass pot eseet and te enable the plungertorisequickly. Theringllismerely' slipped over the plunger and secured thereto as by spreading 'the end of the plunger slightly, or by otherwise securing the ring securely on the plimger.

The invention is also applicable to solenoids as in Figure 3 wherein the plunger Il floats freely. The insert I2 is cut oi! so the plunger is limitedinitsrisebythespring ll andstudll. 'Ihe portion 3l on the upper washer extends down slightly more thanin Figure 1 -to ensure iiux flow to lift the plunger il which is made as light in weight as is possible. The ring Il is po-` sitioned about the plunger base.

It is of course readily apparent to those skilled in the art that variousmodifications can be made without departing from the scope of the appended claims.

I claim:

i. Inan alternating current solenoid, a coil having a passage therethrough, magnetic washers at either end of said coil, a solenoid plunger movable through said passage axially upon energization of said coil into engagement with stop means positioned at one end of said passage to align that end of the plunger in a denite single position axially of said passage, said plunger including an inner magnetic member encased at least partially by a non-magnetic member and an outer magnetic member extending substan-V tially between said washers when said plunger engages .said stop, said members being iixedly joined together`into a single unit movable as such, said inner magnetic member engaging said stop means, and a non-magnetic sleeve carried by the plunger and positioned thereon to distribute more evenly flux from one of said wash.

ers adjacent the other end of the plunger and maintain said other plunger end in a single position in said passage whereby humming is absent.

2. In an alternating current solenoid, an electro-magnetic coil having a passage therethrough, magnetic means providing a magnetic path portion of low reluctance about the ends and outside of said coil, a free solenoid core of magnetic material movable in said passage and cooperating with the aforesaid magnetic means to provide a complete first ilux' path for flow of flux upon energization of said coil, a stop of magnetic material positioned at one end of said passage and engaged by said core upon energination oi' said core, said core and said stop having magnetic end portions providing a cooperating tapered projection and a like tapered recess directly en- 8581118 to guide and center and retain the core atlvely cheap and inexpensive electro-magnetic in a nxed location at said one e end only during energization of said coil, shading coil means at said one passage end displacing ux iiowing through said tapered projection and recess to provide a second magnetic path through said stop and core out of phase with the iiux traversing said first path during coil energisation, means effective to isolate magnetically at least one of said tapered end portions from said rst iiux path and limit now through said end portions ot residual nux from said first path when said cod is deenergized whereby stickingof said 'core against said stop is obviated upon deenergization of said ooil, and a non-magnetic sleeve carried by the core' adjacent the other passage end to distribute more evenly flux passing to said coreatssidotherpassageendfromsaidmagnetic meansand maintain said core in a single position in said passage whereby humming is absent when the coil is energized and the core is against said stop.

energization of said coil, a stop of magnetic ma-v terial positioned at one end of said passage and engaged by said core upon energization of said core, said core and said stop having magnetic end portions providing a cooperating tapered pro-v jection and a like tapered recess directly engaging to guide and center and retain the core in a xed location at said one passage end only during energization of said coil, said tapered projection and recess each being relatively small in total cross-sectional area as compared to the cross-sectional area of said core, said recess beging relatively shallow as compared to the length of said core, shading lcoil means at said one passage end displacing flux owing through said tapered projection and recess to provide a second magnetic path through said stop and core out of phase with the flux traversing said rst path during coil energization, means effective to isolate magnetically at least one of said tapered end portions from said rst ux path and limit flow through said end 'portions oi residual flux from said rst path when said coil is deenergized whereby sticking of said core against said stop is obviated upon deenergization o! said coil, and

a non-magnetic sleeve carried by the core adjacent the other passage end to distribute more evenly ux passingr to said core at said other passage end. from said magnetic means and maintain said core in a single position in said passage whereby humming is absent when the coil is energized and the core is against said stop.

4. An alternating current solenoid comprising a current carrying coil having an axial passage therethrough, a unitary structurally integral magnetic plunger disposed within said passage and attracted to a raised position by the ow of an alternating current in the coil and released to a lower position upon cessation of the alternating current, and fixed means for carrying an alternating magnetic flux and transmitting the same to the ends of the plunger said means comprising a magnetic stop at the top of the passage, said stop and upper end of the plunger having, as anti-hummingk means, shading coil means and complementary nesting surfaces; said fixed means further comprising an annular magnetic member at the lower end of the coil surrounding the lower end portion ofthe plunger, separated from v the plunger by an annular air gap and conducting an alternating magnetic flux to the plunger in a direction generally radial of the plunger axis, and, as anti-humming means at the lower end of the plunger, a nonmagetic conducting cylinder interposed in said air gap and carried by the lower end of the plunger and forming a closed electric circuit of low resistance in paths around the flux and distributing the flux substantially to eliminate humming thereat.

WILLIAM A. RAY. 

